The Impact of Corrosion Inhibitors on Relative Permeability of Water Injector and Production Well Performance

Abstract

Abstract In many oilfields with carbonate and sandstone reservoirs corrosion inhibitors are applied to control corrosion within production wells via continuous or batch treatments of the tubing and in water injection wells (seawater/aquifer and produced water) via continuous injection. The corrosion inhibitors within these formulations are fundamentally designed to control corrosion at the lowest treatment rate possible with little thought given to their potential impact on the wettability of the reservoir rock if they were to contact it. This paper will present details from a set of corefloods which look at seawater and produced water re injection (PWRI) under matrix flow conditions within carbonate and sandstone cores. The observed stimulation in the water injection tests suggests that it is possible for the injector wells to take more water due to the interaction of the corrosion inhibitors tested for both matrix types. The corrosion inhibitor solution when applied to cores which had been solvent cleaned showed stimulation (increased brine permeability) suggesting that the chemical interacted with mineral surfaces rather than improved brine permeability due to change in residual oil saturation within the pore space of the rock. Results for corrosion inhibitor application to production wells where the chemical is allowed to flow out of the production tubing during "batch" tubing treatments are also presented. The production well data is in marked contrast to the water injector results, the change in wettability in both carbonate and sandstone observed with the introduction of the corrosion inhibitors tested would reduce oil production and increase water production due to the change in relative permeability observed with corrosion inhibitor adsorption onto the mineral substrate (both silicates and carbonate). The paper outlines the mechanism of stimulation for water injection wells and highlights the damage potential of a flow assurance challenge that is receiving a significant amount of focus within both onshore and offshore fields at this time.